Remove Ken from docs maintainers (he's busy on other things)

Docker-DCO-1.1-Signed-off-by: Solomon Hykes <solomon@docker.com> (github: shykes)
Remove myself as sole maintainer of api reference docs.

Please still ping me before changing APIs :)

Docker-DCO-1.1-Signed-off-by: Solomon Hykes <solomon@docker.com> (github: shykes)